From 9790dc65026c22f26ea6e247c5506b88f36691a4 Mon Sep 17 00:00:00 2001
From: Astatin <git@astatin.live>
Date: Fri, 9 Aug 2024 21:19:36 +0900
Subject: Turn off screen during initialization to be compatible with sameboy

---
 Makefile          |  6 ++++++
 bunny.gbasm       |  4 +++-
 definitions.gbasm |  1 +
 init.gbasm        | 30 ++++++++++++++++++++++--------
 main.gbasm        |  8 ++++++--
 tiles.gbasm       |  2 +-
 6 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/Makefile b/Makefile
index a0222e4..19d678f 100644
--- a/Makefile
+++ b/Makefile
@@ -9,5 +9,11 @@ build/main.rom: main.gbasm
 run: build/main.rom
 	gb $<
 
+sameboy: build/main.rom
+	sameboy build/main.rom
+
+gearboy: build/main.rom
+	gearboy build/main.rom
+
 clean:
 	rm -rf build
diff --git a/bunny.gbasm b/bunny.gbasm
index c6a06de..04d14a9 100644
--- a/bunny.gbasm
+++ b/bunny.gbasm
@@ -7,7 +7,7 @@ Initialize_Bunny:
 	LD $reg_viewport_x, A
 	LD A, $50
 	LD $mem_bunny_x_px, A
-	LD A, $50
+	LD A, $48
 	LD $mem_bunny_y_px, A
 	RET
 
@@ -178,6 +178,7 @@ Display_Bunny: ; X position in $81, Y position in $80
 	LD A, B
 	LD (HL+), A
 	LD A, E
+	INC A
 	LD (HL+), A
 	LD A, D
 	LD (HL+), A
@@ -193,6 +194,7 @@ Display_Bunny: ; X position in $81, Y position in $80
 	LD (HL+), A
 	LD A, E
 	XOR $02
+	INC A
 	LD (HL+), A
 	LD A, D
 	LD (HL+), A
diff --git a/definitions.gbasm b/definitions.gbasm
index 8e9ea5b..fdefee8 100644
--- a/definitions.gbasm
+++ b/definitions.gbasm
@@ -1,5 +1,6 @@
 .DEFINE reg_joypad ($00)
 .DEFINE reg_lcd_controller ($40)
+.DEFINE reg_lcd_status ($41)
 .DEFINE reg_viewport_y ($42)
 .DEFINE reg_viewport_x ($43)
 .DEFINE reg_bg_palette ($47)
diff --git a/init.gbasm b/init.gbasm
index 20a5461..79d09f6 100644
--- a/init.gbasm
+++ b/init.gbasm
@@ -5,7 +5,7 @@ VBlank:
 
 .PADTO 0x0100
 Start:
-	JP =Empty_VRAM
+	JP =Initialize_RAM
 
 .PADTO 0x0104
 Nintendo_Logo: ; The Nintendo logo must be stored in bytes 0x104-133
@@ -18,10 +18,29 @@ Checksum: ; The bytes 0x134-0x14d need to add up to 0xe7 (= 0xff - 0x19)
 	.DB $00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
 	.DB $00,$00,$00,$00,$00,$00,$00,$00,$00,$e7
 
+Initialize_RAM:
+Empty_WRAM:
+	LD HL, $C000
+	Empty_WRAM.loop:
+		XOR A
+		LD (HL+), a
+		LD a, $D0
+		CP h
+		JR NZ, =Empty_WRAM.loop
+
+Wait_VBlank:
+	LD A, $reg_lcd_status
+	AND $03
+	CP $01
+	JR NZ, =Wait_VBlank
+
+	; LCDC
+	XOR A
+	LD $reg_lcd_controller, A
+
 Empty_VRAM: ; (Clear screen)
 	LD hl, $VRAM_start ; We set the HL register to the start of VRAM
-
-Empty_VRAM.loop:
+	Empty_VRAM.loop:
 		XOR A
 		LD (HL+), a 						; We set the memory pointed to by HL to 0 and increase HL
 		LD a, $a0
@@ -36,11 +55,6 @@ Empty_VRAM.loop:
 	LD A, $e4
 	LD $reg_obj0_palette, A
 	
-	; LCDC
-	LD A, $reg_lcd_controller
-	OR $06
-	LD $reg_lcd_controller, A
-
 	; Interrupts
 	LD A, $01
 	LD $reg_interrupt_enable, A
diff --git a/main.gbasm b/main.gbasm
index 7ef75fd..7f30a8e 100644
--- a/main.gbasm
+++ b/main.gbasm
@@ -3,9 +3,13 @@
 
 Entrypoint:
 	CALL =Load_Tile
-	CALL =Initialize_Bunny
 	CALL =Load_Map
-	
+	CALL =Initialize_Bunny
+
+	; LCDC
+	LD A, $97
+	LD $reg_lcd_controller, A
+
 	EI
 	Wait_for_VRAM.loop:
 	HALT
diff --git a/tiles.gbasm b/tiles.gbasm
index 4769e2a..bba72b9 100644
--- a/tiles.gbasm
+++ b/tiles.gbasm
@@ -62,7 +62,7 @@ memcpy: ; src = DE, dest = HL, n = BC
 	RET
 
 Load_Tile:
-	LD HL, $8010
+	LD HL, $8020
 	LD DE, =OBJ_Tile_Image_Data
 	LD BC, $00c0
 	CALL =memcpy
-- 
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